Alfalinux is a Slackware-like Linux distribution on two floppy disks. It doesn't have any restrictive/reduced/remade system parts and contains all the required applications for disk operations, recovering, and networking.

Argante is a fully operational, virtual environment for effective, secure, and accurate development of network appliances and other solutions (distributed routers, heterogenic, and self-adapting clusters).

"Ball", the Byzantine Askemos Language Layer,
is an intrusion resistant and incorruptible,
autonomous distributed operating system.
It provides application programmers with
continuations, messages, and rights management
on top of a peer-to-peer network resisting byzantine failures of network nodes. The API significantly raises the level of abstraction in comparison with other operating systems: there are very few system calls, and these are expressed in XML. An alternative understanding of Askemos is that of an XML object database with stored procedures.

BasicLinux is a mini-Linux distribution designed
specifically for old PCs. It provides a slim
2.2.26 kernel, a user-friendly shell and a good
assortment of utilities. It includes a Web
browser, a comm program, an email client, a telnet
client, wget, DHCP, and dial-up PPP. It also
includes a small footprint GUI, and is able to run
remote X (via network) with as little as 4 MB RAM.
BasicLinux is particularly suitable for old
laptops: it comes with PCMCIA capability and
includes the MagicPoint presentation program.

Circle Mud Linux is a three-disk mini-distribution for running the Circle MUD Server. It is based on libc5. It is also a good distribution for MUD players who can use it to quickly and temporarily turn any PC into a MUD console.

Coyote Linux is a mini distribution designed for
setting up network utility services such as
Internet connection sharing, firewalling, or
wireless access points. The goal is to make it as
quick and easy as possible to set up a Linux
system with only a minimal amount of Linux knowledge.

Debian is an operating system for your computer that consists only of Free Software. It uses the Linux kernel, and a large part of the basic tools that fill out the operating system come from GNU, which are also free. It comes with thousands of packages.

DragonLinux is an Internet-ready distribution which is only 150MB installed. It is a fully-functional UMSDOS/Loopback hybrid complete with networking tools, a compiler, X-Windows, KDE, and documentation.

eCos (Embedded Configurable OS) is an open source, configurable, portable, and royalty-free embedded Real Time Operating System. It is written in C++, provides all the usual OS things. You configure the OS so that the parts you don't need aren't loaded to the embedded system. eCos is released under a modified GPL that allows for its use in embedded systems without having to GPL the embedded application.